Projected 2018 sales: $1.295 billion
2012 sales: $4.027 billion

The market for multiple sclerosis drugs is expected to reach nearly $20 billion by 2020, and as Teva ($TEVA) is finding out, Big Pharma is none too eager to let Copaxone soak up all those profits without some competition. With sales of over $4 billion a year and 20% growth in the last earnings period, the drug is flying high, but that competition is heating up--and with analysts estimating Copaxone as responsible for upward of 40% of the company's overall profits, Teva has a lot to lose.

The company is working hard to fend off branded competitors, whose makers are trying to carve out a niche for their products. Oral MS treatments, such as Biogen Idec's ($BIIB) Tecfidera and Aubagio from Sanofi's ($SNY) Genzyme subsidiary, have grabbed market share from injectables like Copaxone. Sanofi undercut Teva by pricing Aubagio at $45,000 a year, 7% less than Copaxone, to break into the market. And so far, it has worked: In March, the head of MS for Genzyme said that in Aubagio's first 6 months, it had been prescribed by 80% of all MS specialists, with most of those switching over from Copaxone.

In response, Teva has petitioned the FDA demanding that all prospective MS treatments be subject to review by the agency's advisers, citing patient safety concerns. For example, Teva alleged that Biogen's new pill Tecfidera, when it was inching toward FDA approval, could be associated with other serious safety risks like kidney problems. And Teva has reason to be worried: It will also soon have a battle with generics going on, with Copaxone going off patent in 2015.

For more:
Eyeing Biogen drug, Teva demands review for new MS meds
Aubagio approval sets Sanofi up with possible blockbuster
Teva's patent victory on Copaxone boosts franchise long-term
Copaxone patent fight set for court Sept. 7